Useful range of conventional electric vehicles is limited by battery capacity. To extend range, hybrid vehicle concepts incorporating an engine and a generator have been considered. One drawback of such concepts, however, is the weight and volume penalties of carrying the engine and generator with the vehicle, particularly where the vehicle is to be used primarily for short-range daily commutes with only occasional need for extended range. Therefore, a need has been recognized for attaching an auxiliary power unit or another electrically active device to the rear of an electric vehicle when it is desirable to extend the useful range of the vehicle and to detach the auxiliary power unit or another electrically active device from the rear of the electric vehicle when additional useful range is not needed. This device may include a tank of fuel and either a fuel cell or an engine and an electrical generator, so it may have a substantial mass, fifty kilograms, for example, and therefore require a robust structural connection to the vehicle to remain in place during vehicle operation, especially over rough roads, where the connection may need to bear forces several times the weight of the device. This device may produce a level of electrical power that is sufficient to meet the average power demand during sustained driving over long distances, ten kilowatts, for example, so a high-capacity electrical connection may also be required.
The use of trailer hitches is fairly common for mechanically attaching accessories such as trailers to the rears of vehicles. In one common embodiment, a hitch receiver is permanently affixed to the frame of a vehicle and comprises a female body with a square opening for receiving and mechanically coupling with a mating, square, male element of a trailer hitch. The trailer hitch may comprise a ball for hitching a trailer to the vehicle. Such a trailer hitch, which is configured for mating with a hitch receiver, is often called a “receiver hitch”, to distinguish it from a hitch that itself is affixed to a vehicle, such as by welding or bolting. The hitch receiver may alternately be used to attach a cargo rack to the vehicle configured for carrying luggage, bicycles, skis, or other equipment.
To provide electrical power to the trailer or other accessories attached via the hitch receiver, an electrical connection pad is often mounted to the rear of the vehicle near the hitch receiver and apart from it. Such electrical connection pads provide a location where an electrical connector associated with the trailer or other accessory may be electrically coupled with the systems of the vehicle after the trailer or other accessory has been mechanically coupled to the vehicle via the hitch receiver. Alternately, a connector may be permanently attached to the vehicle by only its wires and provide a location where an electrical connector associated with a trailer or other accessory may be electrically coupled.
One common variety of electrical connector associated with a vehicle hitch has a flat or rectangular cross section with a plurality of terminals arranged in one or more rows. Another variety of hitch electrical connector has a generally round cross-section, with its terminals arranged in a circular pattern. Each of these configurations may include between four and seven terminals. In connectors having four terminals, the terminals typically provide a basic electrical connection for providing power to the accessory for activating running lights, turn signals, and brake lights. The fourth terminal provides an electrical ground.
In connectors having five terminals, three terminals power the three lighting functions (running lights, the turn signals, and the brake lights). The fourth terminal provides a ground, and a fifth terminal is provided for electrically deactivating the hydraulic surge brakes of a trailer when backing. Therefore, the fifth terminal is often coupled to the backup lights of the vehicle.
In connectors having six terminals, three terminals power the three lighting functions (running lights, the turn signals, and the brake lights), and the fourth terminal provides a ground. The fifth terminal provides a “hot” lead for charging a battery mounted on the trailer or accessory such as is commonly used with electric trailer brakes, and the sixth terminal facilitates communication of an on/off signal for activating/deactivating the brakes. In connectors having seven terminals, all the functions of the six-terminal connector are provided, and an additional terminal provides for back-up lighting.
Notably, each of these connectors are mounted externally to the hitch receiver and configured to provide power from the vehicle to the trailer at current levels suitable to power vehicle lighting or for trickle-charging a battery or for providing a signal for activating or deactivating a brake system. Moreover, these conventional connectors are typically configured for shielding a twelve-volt potential against inadvertent grounding. Unfortunately, such accessory connectors are typically not designed and configured for carrying electrical power from an auxiliary power unit to the vehicle, particularly at power levels suitable for charging or powering the vehicle. In addition, the higher voltages (e.g., up to 400 volts) associated with the power systems of electric vehicles require greater shielding than that provided by conventional connectors. Finally, the requirement to employ an electrical connector separately from, and in addition to, the mechanical attachment provided by the hitch receiver adds an element of complexity and unreliability to the process of attaching and detaching such an auxiliary power unit.
Accordingly, it is desirable to have an electrical connector that can provide the power and signal carrying capabilities required by electric vehicles such as for controlling an auxiliary power unit and for carrying power from the auxiliary power unit to the vehicle in a convenient, reliable and safe manner. It would further be advantageous to have an electrical connector configured for structurally supporting an auxiliary power unit electrically and mechanically coupled to the rear of a vehicle. It would also be advantageous to have an electrical connector that is configured for serving as a mechanical trailer hitch receiver.